1. Technical Field
The present disclosure relates to a signal reception circuit and an isolated signal transmission device. These are, for example, applied to a gate driver circuit that drives a gate terminal of a semiconductor switch.
2. Description of the Related Art
A gate driver circuit is a circuit that drives a semiconductor switch. The gate driver circuit controls the semiconductor switch on and off by applying a gate voltage to the gate terminal thereof. One high-voltage semiconductor switch is, for example, the insulated gate bipolar transistor (IGBT), which is a type of power semiconductor device. A typical gate driver circuit has a P-type transistor and an N-type transistor at the output part thereof. The semiconductor switch is turned on when P-type transistor operates, and is turned off when the N-type transistor operates. When the semiconductor switch is turned off, the gate current is withdrawn from the semiconductor switch.
A gate driver circuit includes a primary side into which a control signal is input into the gate driver circuit, and a secondary side from which a driving signal is output to the semiconductor switch. In such a gate driver circuit, the reference voltage on the secondary side is extremely high. Therefore, the direct current (DC) component must be isolated, or in other words the signal ground must be isolated, between the primary side and the secondary side. For this reason, a known gate driver circuit has a signal isolator, or a contactless signal transmitter, which is able to realize isolation of the DC component between the primary side and the secondary side. Further, the known gate driver circuit requires an isolated power source for driving a semiconductor switch, separately. The isolated power source, however, leads to increased circuit size. If the gate driver circuit were able to not only isolate the gate signal, but also supply isolated power to the gate of the semiconductor switch, an external isolated power source would be unnecessary, and a more compact gate driver circuit would be possible.
Japanese Unexamined Patent Application Publication No. 2008-067012 discloses a power transmission system using an open-ring electromagnetic resonance coupler for the contactless signal transmitter.